The present invention relates to an apparatus for displaying a travel path in which the current position of a moving body such as an automobile is given on a road map appearing on a screen.
In an attempt to prevent a driver from losing his way when travelling in an unfamiliar place, an apparatus for displaying a travel path has been proposed in which the current position of the driver's automobile is sequentially estimated in terms of X- and Y- coordinates by carrying out algorithmic operations on the automobile's running distance and direction of travel. The automobile's running distance and direction of travel are determined by an associated distance meter and direction sensor, respectively. The current position of the driver's automobile then appears in the form of a dot on a road map appearing on a screen.
A cumulation of errors in determining the running distance and direction of the automobile will result in an incorrect indication of the automobile's current position. In some instances, an incorrect current position will cause the display dot to depart from all roads appearing on the driver's screen such that the driver will be unable to determine the road on which his car is running.
Past attempts to solve this problem have proposed comparing a travel trace having sequentially renewed estimated current car positions thereon with all the roads in the vicinity of the last estimated current car position on the screen to find the roads having similar patterns. This is accomplished according to the conventional pattern matching process. The road which is closest in shape to the travel trace is then selected as the "true" road on which the car is running. The dot image of the last estimated current car position is then put on what appears to be the true road.
This correction, however, will require much time if many roads and branch roads appear in the vicinity of the last estimated current car position because a pattern matching must be carried out for each of these selected roads.